Since last year he has been spending one day a week working for a Government think-tank on health.

Mr Elson, 56, became chief executive in February 1998 after joining the council 10 years earlier as social services director.

He said: "Kirklees is regarded as one of the leading local authorities in the country.

"I believe the council is extremely well positioned to go beyond that and become the top local authority in the country.

"While it would have been good for me to be part of that, I think it is the appropriate time for someone else to take on the challenges that lie ahead."

He revealed he had initial talks with the leaders of the political groups some time ago about leaving.

But they had asked that he stay until last month's local elections.

A nationwide hunt is to be launched to find Mr Elson's replacement.

His one-day-a-week job for the Government is on an investigation into the factors that mean that the life expectancy of a child born in some parts of the country is many years less than in other more affluent areas.

A highlight of his career in Kirklees came in 2002 when the council was the only one in Yorkshire and Humber to be rated as an `excellent' council in an independent study by the Audit Commission.

The council maintained the position last year.

Mr Elson said: "We have a highly effective management structure in place and a workforce commitment within the council which has demonstrated it is well capable of meeting challenges and continuing to improve services."

He entered local government at the end of the 1960s and for many years was involved in social work in Birmingham.